Organic light emitting diode (OLED), as a new generation of display device following liquid crystal display (LCD), has become one of research hotspots in recent years because of its advantages such as quick response, plentiful colors, lower power consumption, and wider viewing angle.
However, considering a difference in refractive indexes between an organic luminescent material (1.7-1.8), a substrate (1.5) in the OLED and the air (1.0), the light will be subjected to, in a waveguide mode, a total reflection between a luminescent layer and a transparent electrode as well as a total reflection in the glass substrate, which may cause light loss; in addition, part of the light will be lost, in a surface plasma mode, at a surface of the electrode. Therefore, actually, only about 20% of the light can be emitted into the air. To improve light extraction efficiency, it usually disposes a scattering means or a lens at an outer surface of the substrate so as to extract the light trapped in the glass, which, however, may cause halo effect and thus is only suitable for lighting but cannot meet requirements of display technology.